Linking Electronic Transport through a Spin Crossover Thin Film to the Molecular Spin State Using X-ray Absorption Spectroscopy Operando Techniques

Abstract

One promising route toward encoding information is to utilize the two stable electronic states of a spin crossover molecule. Although this property is clearly manifested in transport across single molecule junctions, evidence linking charge transport across a solid-state device to the molecular film's spin state has thus far remained indirect. To establish this link, we deploy materials-centric and device-centric operando experiments involving X-ray absorption spectroscopy. We find a correlation between the temperature dependencies of the junction resistance and the Fe spin state within the device's [Fe(HB(pz))(NH-phen)] molecular film. We also factually observe that the Fe molecular site mediates charge transport. Our dual operando studies reveal that transport involves a subset of molecules within an electronically heterogeneous spin crossover film. Our work confers an insight that substantially improves the state-of-the-art regarding spin crossover-based devices, thanks to a methodology that can benefit device studies of other next-generation molecular compounds.

Anomalous Light‐Induced Spin‐State Switching for Iron(II) Spin‐Crossover Molecules in Direct Contact with Metal Surfaces

“…Them aximum proportion of HS molecules that we have been able to switch for those molecular layers in direct interaction with Cu metal surfaces is no more than 20 %. This has been already observed for similar systems [30] or in devices [35] and has been ascribed to structural changes or degraded molecules, [36] presumably modified by the X-ray beam. Although this latter explanation is likely and depends on both the molecular moieties and the X-rays fluence,w ebelieve that this partial switching is also induced by the molecule-substrate interactions.…”

Anomalous Light‐Induced Spin‐State Switching for Iron(II) Spin‐Crossover Molecules in Direct Contact with Metal Surfaces

“…Them aximum proportion of HS molecules that we have been able to switch for those molecular layers in direct interaction with Cu metal surfaces is no more than 20 %. This has been already observed for similar systems [30] or in devices [35] and has been ascribed to )and 850 nm (32 mWcm À2 ). The usual LIESST is observed for 405 nm ( 1 MLCT excitation) and 635 nm ( 1 A 1 to 1 T 1 excitation), while the reverse LIESST is observed for 850 nm ( 5 T 2 to 5 Ee xcitation).…”

“…The maximum proportion of HS molecules that we have been able to switch for those molecular layers in direct interaction with Cu metal surfaces is no more than 20 %. This has been already observed for similar systems or in devices and has been ascribed to structural changes or degraded molecules, presumably modified by the X‐ray beam. Although this latter explanation is likely and depends on both the molecular moieties and the X‐rays fluence, we believe that this partial switching is also induced by the molecule‐substrate interactions .…”

Spin-Crossover Complexes in Direct Contact with Surfaces

“…The spin state may be determined from the transport properties as shown above and demonstrated in several break junction, nano gap, vertical junction, and transistor experiments [12,14,43,56,83,[96][97][98][99]. However, the spin-state identification is not straightforward.…”